Abstract
Adipose tissue, in particular epicardial adipose tissue, has been identified as a potential biomarker of cardiovascular pathologies such as coronary artery disease (CAD) in the light of its metabolic activity and close anatomic and pathophysiologic relationship to the heart. Our purpose was to evaluate epicardial adipose tissue density at both unenhanced and contrast-enhanced computed tomography (CT), along with CT densities of paracardiac and subcutaneous adipose tissue, as well as the relations of such densities with CAD. We retrospectively reviewed patients who underwent cardiac CT at our institution for CAD assessment. We segmented regions of interest on epicardial, paracardiac, and subcutaneous adipose tissue on unenhanced and contrast-enhanced scans. A total of 480 patients were included, 164 of them presenting with CAD. Median epicardial adipose tissue density measured on contrast-enhanced scans (−81.5 HU; interquartile range −84.9 to −78.0) was higher than that measured on unenhanced scans (−73.4 HU; −76.9 to −69.4) (p < 0.001), whereas paracardiac and subcutaneous adipose tissue densities were not (p ≥ 0.055). Patients with or without CAD, did not show significant differences in density of epicardial, paracardiac, and subcutaneous adipose tissue either on unenhanced or contrast-enhanced scans (p ≥ 0.092). CAD patients may experience different phenomena (inflammation, fibrosis, increase in adipose depots) leading to rises or drops in epicardial adipose tissue density, resulting in variations that are difficult to detect.
Highlights
Epicardial adipose tissue is a metabolically active fat depot located around the heart and within the visceral wall of pericardium [1]
While transthoracic echocardiography enables one to measure epicardial adipose tissue thickness and magnetic resonance imaging allows for the calculation of its volume, computed tomography (CT) permits the estimation of its volume and a density analysis based on CT numbers and their translation into Hounsfield Units (HU) [4]
The density values found for epicardial adipose tissue in this work, significantly higher than those of paracardiac and subcutaneous adipose tissue (p < 0.001 for both) fit well with the notion that the anatomy and physiology of epicardial adipose tissue are different than those of paracardiac and subcutaneous adipose tissue
Summary
Epicardial adipose tissue is a metabolically active fat depot located around the heart and within the visceral wall of pericardium [1]. Epicardial adipose tissue is composed of so-called “beige” adipocytes, which along with brown adipocytes are subtypes of thermogenic fats, and regulate metabolism and homeostasis [2]. Epicardial adipose tissue can be assessed noninvasively via imaging studies. While transthoracic echocardiography enables one to measure epicardial adipose tissue thickness and magnetic resonance imaging allows for the calculation of its volume (and, potentially, multiparametric analysis), computed tomography (CT) permits the estimation of its volume and a density analysis based on CT numbers (obtained through reference to the water X-ray attenuation) and their translation into Hounsfield Units (HU) [4]. Mahabadi et al [9] observed a correlation between epicardial adipose tissue density and the occurrence of myocardial infarction, with patients presenting infarction displaying higher epicardial adipose tissue density values
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